GB1395814A - Percussion tool - Google Patents

Abstract

1395814 Percussive drills ROBERT BOSCH GmbH 5 May 1972 [7 May 1971] 20961/72 Heading B4C In a percussive drill of the kind in which the tool spindle is reciprocated by interaction between notches on opposed annular discs carried by the spindle and housing respectively, one or more additional discs are arranged coaxially inside the housing disc angularly adjustably relative thereto to enable the frequency of the blows to be varied for various drill sizes and speeds. In both embodiments described, the teeth of the or each additional disc may be the same in number or different from those on the housing disc. They may be adjusted to be selectively aligned with or staggered relative to the latter. The additional disc(s) are fixed axially. In the arrangement shown, an additional disc 233 is rotatable with the spindle or is fixed but adjustable through a limited angle within the fixed housing disc 232. This rotation is, controlled in one embodiment, by a pin 254 having flats on its end 255 engageable in a keyhole slot 234<SP>1</SP>. It may be held withdrawn from the slot when the disc 233 rotates with the spindle and only the teeth of the housing disc are effective, be inserted as in Fig. 4a with its teeth in one position relative to those of the disc 232 or in the position of Fig. 4c, for a different position, the juxtapositioning of the inner and outer teeth giving different blow frequencies. In another embodiment Figs. 8-10 (not shown), a rotary handle lifts a stop out of a radial bore in the disc 233 to free it for rotation with the spindle. The housing disc may be angularly adjustable (not shown).